Health - Treatments
By: - at June 8, 2013

How Chemotherapy Treats Cancer

Smiling Kid with CancerA successful cancer treatment has two goals: remove the cancer cells and minimum damage to normal cells. After many centuries of research, doctors have many options for treating cancer: monoclonal antibody therapy, chemotherapy, immunotherapy, surgery, and radiation therapy. The type of treatment used depends on many considerations: general health of the patient, type of cancer, stage of the disease, and grade and location of the tumor. Doctors usually use more than one option for the same treatment. For instance, chemotherapy after surgery has completely removed visible cancer is called adjuvant chemotherapy. Chemotherapy protocols target and destroy cancer cells using drugs. There are various protocols for treating different types of cancer. Normal cells affected during chemotherapy recover after some time. However, the affected normal cells cause side effects. This article describes how doctors use various types of chemotherapy protocols to treat cancer.

Cell Division in Normal and Cancer Cells
Normal and Cancer Cells

Body cells reproduce by subdividing themselves into two or more cells. Various types genes, such as tumor suppressor genes and oncogenes, closely regulate this complex process of cell division. Both normal and cancer cells undergo cell division, a final stage in the cell cycle. The cell cycle starts from resting phase then progresses to active growing phases and finally to cell division (mitosis).

Normal cells stop dividing when they meet cells similar to them, a process called contact inhibition. However, cancer consists of a group of cells that grow abnormally and uncontrollably fast. They do not stop growing when they meet other cells. Consequently, the cancer cells intrude upon and destroy neighboring tissues. Furthermore, cancer cells can spread to other parts of the body through the bloodstream or lymphatic system.

How Chemotherapy Cures Cancer
Chemotherapy cures cancer by stopping the cells from subdividing. The drugs can stop the cell division in two ways. First, they can damage the DNA or RNA that enables the cell to copy itself. Lastly, the drugs can induce cell suicide, apoptosis. Cancer cells immediately die when they cannot divide and the tumor shrinks. The treatment is most effective on cancer cells that divide fast.

Chemotherapy drugs destroy cancer cells in two phases of the cell cycle. First, cell-cycle specific drugs only kill the cancer cells at their mitosis phase. Lastly, cell-cycle non-specific drugs kill the cells before they start dividing. Doctors schedule chemotherapy according to the type of cells, rate of cell division, and the time when the drug is most effective. Therefore, they administer chemotherapy in cycles.

Side Effects of Chemotherapy
Unfortunately, the drugs affect normal cells as well, especially the ones that divide quickly. Affected normal cells regain their health after some time. However, toxicity to normal cells causes serious side effects. Chemotherapy seriously affects normal cells in hair follicles, bowel, stomach, mouth, and blood. Therefore, the side effects of the treatment are hair loss, low blood count, nausea, diarrhea, and mouth sores. Different drugs can cause the side effects in different parts of the body.

Chemotherapy Drugs
There are six types chemotherapy drugs depending on their mode of action. First, alkylating agents kill the cells in their resting phase. Therefore, they are cell-cycle non-specific. Second, plant alkaloids are extracts from certain plant species: Asian Happy Tree, May apple plant, Pacific Yew tree, and periwinkle plant. They attack the cells in their division phase. Therefore, they are cell-cycle specific. Third, ant-tumor antibiotics are extracts from products of some species of streptomyces, a soil fungus. They are active during all phases of the cell cycle. However, they are considered cell-cycle specific.

Chemotherapy Drugs and Vials

Fourth, anti-metabolites are similar to cell contents. They disable the ability of the cell to divide when the cell absorbs them. They are active at very specific phases of the cells. Therefore, they are cell-cycle specific. Fifth, topoisomerase inhibitors work by interfering with activity of topoisomerase enzymes. These enzymes enhance the manipulation of the DNA structure to enable self-copying necessary for cell division. Lastly, there are many other unique types of chemotherapy drugs. Some of the drugs overlap the groups.

How Doctors Administer Chemotherapy Treatments
Many factors determine type and length of chemotherapy treatment. These factors include the type of cancer, severity of the disease, types of drugs administered, expected side effects of the drugs, expected recovery time from the side effects, previous cancer treatments, general health of the patient, and preferences and goals of the patient. Doctors use biopsy specimen to perform clinical trials before they begin the treatment. The trials enable the doctors to determine the best treatment schedule. They compare trial results from different schedules to find the most effective and well-tolerated one. Furthermore, the schedule selected should have the least side effects.

Generally, doctors administer chemotherapy treatments in cycles. This enables the drugs to attack the cancer cells when they are most vulnerable. Furthermore, breaks within one cycle of treatment allow affected normal cells enough time to recover. The treatment can consist of a single or combination of several drugs.

One-month treatment comprises one cycle. For instance, thirty daily treatments or two bi-weekly treatments comprise one cycle. Within one cycle of treatment, doctors can administer the drugs on a single day, many consecutive days or bi-weekly. A single administration of the drugs can take several minutes, hours, or days. You may be an inpatient or outpatient during the treatment.

Doctors can administer chemotherapy drugs in six different ways depending on the location of the disease. First, they can apply chemotherapy creams or gels to the skin to treat skin cancer. Second, they can administer the drugs directly to a particular part of the body. For instance, in intrathecal chemotherapy, they can administer the drugs directly to the central nervous system. Third, they can administer the drugs directly on to the visible cancer or the place where they surgically removed a cancer. For instance, they can inject the drug directly into the cancer. Forth, they can infuse the drug into a vein. For instance, the doctor can insert a tube into a vein in the arm to give an intravenous injection: they attach a needle to the tube. Fifth, some chemotherapy drugs are in the form of tablets, capsules, or pills. Lastly, doctors can administer the drug as a simple injection.

Duration of Chemotherapy Treatments
The clinical trials done before treatment determine the number of cycles required for the full treatment. Treatment of some cancers can take up to twelve cycles: leukemia, Hodgkin and non-Hodgkin lymphoma, and cancers of the testis. Doctors usually administer adjuvant chemotherapy for four to six months to complete treatment of colon and breast cancers.

Girl waiting in Hospital Bed

It is easy to monitor the progress of treatment of a visible cancer. Therefore, the number of cycles required for full treatment will depend on how the disease responds to the treatment. The treatment should continue for one to two cycles after the cancer disappears to ensure elimination of all microscopic disease. If it shrinks but does not disappear, treatment should continue as long as the body can tolerate it and as long as the disease does not regenerate. However, doctors stop the treatment if the disease regenerates. They can use a different drug if the patient allows chemotherapy to continue. Otherwise, the doctors will stop chemotherapy treatment and instead focus on making the patient comfortable.





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